Method of testing insulated wires



(No Model.)

R. VARLEY, Jr. METHOD 0E' TESTING INSULATED WIRES. No. 464,125. PatentedDeo. 1.1891.

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I UNITED STATES PATENT OFFICE'.

RICHARD VARLEY, JR., OF ENGLEWOOD, NE'W JERSEY.

METHOD OF T ESTING INSULATED WIRES.

SPECIFICATION forming part of Letters Patent No. 464,125, dated December1, 1891.

Application filed February 10, 1891. Serial No. 380,970. (No model.)

To all whom, it may concern:

Be it known that I, RICHARD VARLEY, J r., a citizen of the UnitedStates, residing at Englewood, in the county of Bergen and State ,of NewJersey, have invented certain new and useful Improvements in Methods ofTest.

ing Insulated Wires; and I do hereby declare the following to be a full,clear, and exact description of the invention, such as will enableothers skilled in the art to whichit appertains to make and use thesame.

This invention relates to a method of testing insulated Wires, and hasfor its object a rapid location of minute faults in insulation.

In covering electric conductors with insulatin g material it frequentlyhappens that particles of dust or other foreign matter lodge upon theinsulating material or otherwise become incorporated Within it, or thatthe insulating material contains line cracks or irregularities inthickness which lower its insulating power. A very large percentage ofwires after being coated with insulating material contain such faults.It is a great desideratum to be able to locate them expeditiously andefficiently. Various modes of testing have heretofore been resorted tobut many of them require too much time for use where a large number ofcoils of wire must be tested. I have discovered that if an insulatedwire be connected to one terminal of an electric circuit the otherterminal of which is placed in close relation to the insulating coveringthroughout its length, and the circuit be charged with a current of highpotential, a ash will be exhibited at such point or points of theconductor as are within the range of disruptive discharge. My method oftesting, which I call a flash test, is based upon this discovery.

My invention therefore consists in charging a circuitone terminal ofwhich is connected with the wire to be tested and the other n terminalof which is placed in close relation sulation exists.

to the insulating covering with a current of sufficient electro-motiveforce to produce a flash at the point or points where faulty in- Thebest mode of bringing I the terminals of the circuit into the properrelationto create the flash is to surround the insulated covering with aduid-conductor, such as Water, before charging the circuit.

My invention therefore, more specifically considered, consists incharging a circuit one terminal of which is connected with the insulatedwire and the other terminal of which is connected with a fluid-conductorsurrounding the insulating covering with a current of sufiicientelectro-motive force to produce a flash. at points of weakness. I findthat better re- 6o sults are produced when the circuit is charged withan alternating or reversed current than ywith a current of continuousdirection.

My invention further involves other features which will hereinafter bedefinitely in- 6 5 dicated in the claims.

In the accompanying drawings, which illustrate an organization ofapparatus by which my method may be carried into effect, Figure 1 is adiagrammatic illustration. Fig. 2 is aA 7o sectional view-of the tank,showing a coil in position. Fig. 3 is al diagrammatic View of thecut-out.

Dy represents a dynamo-electric generator or other source of electricenergy, in the circuit of which is interposed a series of coils ofinsulated wire C C O, which are t be tested. As illustrated in thedrawings, asource of direct current is used and a current-reverser O Ris introduced to produce periodical re- 8o versals of current. Oneterminal of the circuit is connected to a binding-post B and the otherterminal is electrically connected with a body of water contained Withinthe tank T. One or both terminals of the coils of wire C 8 5 C O areinserted between two metallic bars E E, supported in posts on the woodenbeam F, supported on the tank, thebars being electrically connected withpost B, or the connections may be madein any other manner. 9o Thus thecircuit between the Wire forming the coils and the water is incompleteunless leakage should exist through the kinsulating covering. If now thecircuit be charged with a current of from fifteen hundredv to two 9 5-thousand volts and the current reverser caused to operate, a flash willbe seen in the Water at that point or points of any of the coilsimmersed therein where the insulating covering is insufficient to resistsuch a charge, roo

such a flash being probably due to a disruptive discharge from the Wireto the Water. The current-reverser is preferably caused to operate at aspeed of about sixty reversals per minute. If after such flash isdeveloped the cu rrentbe continued, the insulation would rapidly bedestroyed, and in order to prevent such a result I interpose in thecircuit, asindicated at C O in the drawings, any suitable form ofelectro-magnetic or other cut-out device thrown in to operation bythecurrent passing through the circuit when the arc or flash is developed.

Any suitable device which will automatically open the testing-circuitwhen the flash occurs may be used as a cut-out. The instrument I prefer,however, is a circuit-breaker,-

controlled by the relaydescribed in my appigcation, Serial No. 380,968,tiled February l0, l l. l

The operation ofthe cut-out will be understood on reference to Fig. 3 ofthe drawings, where R is the relay in the testing-circuit, which circuitis normally held closed by an armature a. The armature of the relay has'a pivoted contact-arm l?, which lags, by reason of its inertia, whenthe armature is attracted, and does not therefore vclose the lo'c'alcircuit unless the current through the relay has a definite duration. Byreason of this lagging the local circuit will not be closed under thecharge and discharge of the reverse currents in the testing-circuit ifthe insulation be perfect, inasmuch as no current will flow, and

the onlyeffect produced in the circuit will be a static charge. Thestatic chargewill be sufcient to affect an ordinary relay if delicatelyadjusted, and therefore some provision is necessary to prevent theoperation of the relay underthe static eect. The lagging-armaturedescribed accomplishes this result, inasmuch as the brief effect due tothe static charge does not last long enough to hold up the armatureuntil the lagging contact b is brought into engagement with itsco-operating contact. However, if a leak should occur through the Waterin the testing-tank by reason of insufficient insulation a current willflow and will actuate the relay, close the local circuit, and thusliftthe armature a away from contact .r y, vopening the testing-circuit.'It will thus be seen that the lagging contact renders the Vcut-outapparatus inactive except when a deficiency in insulation in the wirebeing tested exists. Aweight on the armature Va is adjusted so that itnormally holds the testing-circuit closed. When the armature is tilted,the weight is thrown past the center and holds the circuit open, thusacting as a cut-out.

The coil or coils which show a Hash are removed from the tank and theoperation is repeated with the remaining coils. Such coils as do notexhibit a flash are subjected to other tests' to locate bare spots orother points of extremely low insulatingpowerby other methods. The coilsresponding to the flash test,

the charging-circuit.

which form a very large proportion of the number of coils tested, arethen subjected to a similar mode oftesting, in which'a mechanical switchmanipulated by the operator is used to cut on or off thetesting-current. While conducting this operation the operatormanipulates the coils and by separating the convolutions locates theparticular spot in the coil at which the flash occurs, which he marks in.any suitable manner, so that the fault may be repaired. As indicated inthe drawings, the several coils are in multiplearc relation to Theymight also be arranged in series.

In lieu of the direct current and currentreverser a pure alternatingcurrent of slow alternations might be employed.

Having thus described my invention, whatl claim as new, and desire tosecure by Letters Patent, is'- Y `1. The method of testing an 'insulatedwire, which consists in connecting the wire to one terminal of anelectric circuit, bringing the other terminal into close relation to theinsulating-covering throughout its length, so as to be e'quidistant fromall parts thereof, and charging the circuit wit-h a current of highpotential, lwhereby 'a flash will be caused where the insulation isbelow a definite standard.

2. The method of testing an insulated wire, which consists insurrounding the insulatingcovering with water oroth'er liquid-conductor,connectingv the wire and water with the terminals of an electriccircuit, and charging the circuit with aucurrent of 'a potential tocreate a disruptive Adischarge through the insulation when it is bel-0Wa definite standard.

8. The method vof testing 'an insulated wire, which consists insurrounding the insulatingcovering with a fluid-conductor, connectingthe wire and such Jduid-conductor with the terminals of an electriccircuit, and charging the circuit with an alternating or reversecurterminal of an electric circuit, connecting a huid-conductor'surrounding acoil of thewire with the other terminal of ythe circuit,'charging such circuit witha hi gh-potential current, and periodicallyreversing the direction 'of charge in the insulated iwire during thetest.

6. The method of testing an insulated Wire, which consists in`connecting a wire with one terminal of an electric circuit, connectinga IIO fluid conductor surrounding the insulating- In testimony whereof Iafix my signature in covering with the other terminal'of the oirpresenceof two Witnesses.

cuit, charging such circuit with a 'high-potential current, periodicallyreversing the di- RICHARD VARLY JR' recton of charge in the insulatedwire during Witnesses:

the test, and opening the circuit when a flash ROBT. H. READ,

through the insulation occurs. E. C. GRIGG.

